The invention relates to cameras which can use film having metering perforations and to mechanisms to advance and position said film automatically by sensing said perforations, regardless of the number of times the film advance lever is operated by the picture taker.
Since the advent of film with said metering perforations, solid body or non-expanding cameras with film advance mechanisms actuated by plungers have become well known in the art. These mechanisms are generally typified as follows. After the picture taking button is depressed to expose the film in the exposure gate, the film advance plunger is reciprocally moved to operate a film advance mechanism and advance the film along the film plane past the exposure gate until a succeeding frame of unexposed film is positioned in said gate. As the succeeding frame is positioned, a metering finger detects the presence of the metering perforation in the film by traversing the film plane through the perforation or by moving in the direction of film movement after traversing the film plane. This movement usually locks the film advance means and thereby prevents further reciprocation of the film advance plunger. Locking or preventing movement of said plunger has, on occasion, resulted in damage to delicate camera mechanisms when the unknowing operator mishandles or forces further operation. Depending upon the operation of the particular film metering system, the metering finger often remains in the film metering perforation which has additionally resulted in tearing the film when further film movement is forced beyond that normally allowed.
Mechanisms of this type, which suffer from these deficiencies, are disclosed in the following U.S. patents. U.S. Pat. No. 3,769,891, issued to Hackenburg et al. discloses a film advance mechanism which blocks further rotation when the film metering finger 12d senses a film perforation and causes pallet 16b to engage teeth 104 on film transport member 4 and thereby lock the mechanism to prevent further movement. U.S. Pat. No. 3,747,494, issued to Peters discloses a film advance mechanism which blocks further rotation when the film metering finger 106 senses a film perforation and causes pawl 98 to engage the teeth of ratchet 100 to prevent the rotation of gear 38 and movement of the film advance lever 22.
In addition to the drawbacks described in the prior art, the recent popularity of expanding or so-called push-pull cameras has created a greater urgency for a film advance mechanism actuated by reciprocal motion that does not lock when the film has been advanced the appropriate distance, but rather disengages or disables the film advance mechanism to allow continued reciprocal movement without continued film advance. These cameras expand for picture taking and collapse for easy storage of the camera and the protection of lenses and operating surfaces. Film advance is coupled to the opening and closing of the camera. Therefore, locking the film advance would prevent any opening or closing of the camera once an unexposed frame was positioned in the exposure gate. Further, if the film advance did not disengage once the succeeding film frame was positioned, each opening and closing of the camera would advance the film one frame, wasting many unexposed frames and restricting the utility of the camera. U.S. Pat. No. 3,968,509, issued to Winkler et al. and U.S. Pat. No. 3,825,939 issued to Engelsmann et al. are directed to accomplishing these results, but both require a complex planetary transmission including many difficult and exacting manufacturing and assembly operations. The present invention accomplishes these results with a relatively simple mechanism which is easy to manufacture and assemble and is trouble free in operation.
It is an object of the present invention to provide a camera with a film advance mechanism useable with film having pre-punched positioning perforations.
It is a further object of the present invention to provide a camera with a film advance mechanism which is operated by reciprocal action of a plunger.
It is a further object of the present invention to provide a camera with a film advance mechanism which disengages the film advance mechanism in response to the sensing of a film perforation, yet does not lock the mechanism and still permits reciprocation of the plunger without resulting in further film advancement.